I had a similar problem, where my iPod (4th gen) was not working. The absolute key is that you MUST have your OS recognize it first. If OSX doesn't see it, the adapter won't be able to either.
When I finally got it to work, I ran iPod updater - I told it I wanted to do "Restore". Then, after a few moments, it told me to plug it into the AC Adapter. Then, and only then, will the adapter be able to perform a factory reset (or "restore").